Catalyst composition for selective hydrogenation with improved characteristics

ABSTRACT

This invention relates to heterogeneous catalysts useful for selective hydrogenation of unsaturated hydrocarbons, comprising palladium and optionally a promoter, supported on a substrate, having an uncoated BET surface area of ≦9 m 2 /g, the surface being coated with an ionic liquid. Also described are methods of making the catalysts and methods of selective hydrogenation of acetylene and/or dienes in front-end mixed olefin feed streams.

FIELD OF THE INVENTION

The present invention is related to a catalyst composition for selective hydrogenations, for example for the selective hydrogenation of acetylene in the gaseous phase, comprising a heterogeneous catalyst with a BET surface area of ≦9 m²/g and an ionic liquid applied to the surface of the same. The catalyst composition has improved characteristics such as, for example, improved selectivity in favor of the desired product and better thermal stability.

BACKGROUND OF THE INVENTION

Ethylene and propylene are important monomers for the production of plastics, such as for example polyethylene or polypropylene. Ethylene and propylene are primarily derived from petroleum and petroleum products by means of thermal or catalytic cracking of hydrocarbons. The ethylene or propylene derived with the aid of the cracking process does, however, contain an undesirably high proportion of acetylenic compounds such as acetylene or methyl acetylene (propyne), which can negatively influence downstream ethylene or propylene polymerization. Therefore prior to polymerization the ethylene or propylene must be freed from acetylenic compounds as far as possible.

Typically for the polymerization of ethylene the acetylene concentration must, for example, be reduced to a value of below 1 ppm. For this the acetylene is selectively hydrogenated into ethylene. High requirements are placed on the catalyst and the hydrogenation process. On the one hand, the acetylene must be removed as completely as possible by transformation into ethylene, while the hydrogenation of ethylene into ethane must be prevented, hence the term “selective hydrogenation”. In order to ensure this result, the hydrogenation is carried out within a temperature range that is delimited by the so-called “clean-up” temperature and the so-called “run-away” temperature. In the present context the “clean-up” temperature is understood as the temperature from which an appreciable hydrogenation of acetylene into ethylene is observed, while “run-away” temperature is understood as the temperature at which an appreciable hydrogenation of ethylene into ethane commences. The said temperatures can be determined in that the hydrogen consumption of a defined gas mixture containing acetylene, ethylene, and hydrogen is, for example, measured depending on the temperature.

Palladium shell catalysts, often using silver as a promoter, are primarily used as commercial catalysts for the selective hydrogenation of acetylene into ethylene in hydrocarbon streams. The palladium and the silver are supported on an inert, temperature-resistant substrate. The production of these catalysts is carried out in such a way that suitable salts of palladium and silver, for example palladium nitrate and silver nitrate, are applied to a substrate in form of an aqueous solution (impregnation). The impregnation can take place during separate steps with a palladium compound solution and a silver compound solution. It is, however, also possible to apply the solution of palladium compounds and the solution of silver compounds to the substrate simultaneously during a single impregnation step. The impregnated substrate is then calcined to transform the silver into silver oxide, or the palladium into palladium oxide, and is then subjected to a reduction in order to transfer the catalyst into the active form. During the reaction the silver and palladium are assumed to be transferred into the oxidation state “zero”.

DE 31 19 850 A1 describes a method for the selective hydrogenation of a diolefin with at least 4 carbon atoms in a hydrocarbon mixture. Hydrogenation takes place with hydrogen on a catalyst containing palladium and silver. The silver/palladium weight ratio of the catalyst is 0.7:1 to 3:1. The production of the catalyst is by way of co-impregnation of a substrate with an aqueous solution of palladium and silver salts.

U.S. Pat. No. 5,648,576 A describes a method for the selective gaseous phase hydrogenation of acetylenic hydrocarbons (C₂-C₃) into the corresponding ethylenic hydrocarbons. The production of the catalyst is realized by co-impregnating the substrate with an aqueous solution of the respective metal salts.

EP 0 064 301 A1 offers a catalyst for the selective gaseous phase hydrogenation of acetylene. The production of the catalyst is realized by means of a two-step application of palladium and silver.

EP 0 780 155 A1 describes the production of hydrogenation catalysts, whereby solutions of palladium nitrate and silver nitrate in a nitrogenous acid are used for the impregnation of the substrate.

Apart from the Pd/Ag catalysts described above, a number of further palladium based catalyst are described, which also provide improved selectivity and sometimes also improved activity; the same include Pd/Zn, Pd/Cd, Pd/Ga and Pd/Au. The latter catalyst family is characterized primarily by a high “run-away” temperature.

According to the definition of Wasserscheid and Keim in “Angewandte Chemie” 2000, 112, pages 3926-3945, ionic liquids are salts, i.e. compounds of anions and cations that are externally neutral, which melt at low temperatures, usually at temperatures of below 100° C. Ionic liquids are therefore already liquid at low temperatures. In addition they are generally not flammable and have an extremely low vapor pressure. Due to the high variation range of the structure of their cations and anions, their physical and chemical characteristics can be varied over a broad range.

The concept of coating heterogeneous catalysts with small quantities of an ionic liquid has already been described by Jess et al. and Claus et al. [U. Kernchen, B. Etzold, W. Korth, A. Jess, Chem. Eng. Technol. 2007, 30, 985-994; J. Arras, M. Steffan, Y. Shayeghi, P. Claus, Chem. Commun. 2008, 4058-4060]. In both cases an improved selectivity towards the desired product in the target reaction of the hydrogenation of citral or the hydrogenation of diolefins could be achieved than is possible with the uncoated catalyst. This catalyst family has also been named as SCILL—Solid Catalyst with Ionic Liquid Layer—catalysts by the authors.

US 2008/0269533 A1 describes the selective mono-hydrogenation of conjugated dienes with the aid of supported Pd nanoparticles coated with ionic liquids.

International patent application WO2007/124 896 relates to heterogeneous catalysts having a BET surface area of preferably 10 to 300 m²/g. These catalysts may be covered with an ionic liquid and are used for the selective hydrogenation of unsaturated cyclic compounds.

A catalyst system for the selective hydrogenation of acetylene in the simultaneous presence of ethylene comprising a heterogeneous catalyst coated with ionic liquid has also already been described [M. Ruta, G. Laurenczy, P. J. Dyson, L. Kiwi-Minsker, J. Phys. Chem. C 2008, 112, 17814-17819]. However, these catalysts are prepared with support materials that are not suitable for industrial use, as the production of the same is too costly. The described turnovers are also far from realizable.

With all of the examples described so far support materials with a high specific surface area and a suitable pore volume were used. In order to achieve an even coating of the entire catalyst surface, and thus the best possible effect (selectivity increase etc.) a relatively large quantity of ionic liquid is required (10-17 wt. % in relation to the initial weight of the heterogeneous catalyst). This often results in a substantial pore filling of the catalyst and the reduced activity connected with the same. Ionic liquids are also expensive, which results in substantial additional costs for the overall catalyst formulation.

SUMMARY OF THE INVENTION

There remains a need for further improving the selectivity of Pd/promoter catalysts for the hydrogenation of acetylenic hydrocarbons, while maintaining or even increasing catalyst activity.

It is therefore the object of this invention to provide a catalyst with high selectivity and activity for the hydrogenation of acetylenic hydrocarbons.

Surprisingly it has been found that conventional heterogeneous catalysts with a BET surface area of ≦9 m²/g which are coated with a small amount of an ionic liquid have improved characteristics, such as improved selectivity in the hydrogenation of unsaturated hydrocarbons while retaining high activity.

With the catalyst system of the invention, known pre-formulated catalysts for the transformation of acetylene into ethylene with a BET surface area of ≦9 m²/g are coated with one (or more) ionic liquid(s). The resulting catalyst formulations have a very high selectivity during the hydrogenation of acetylene in ethylene rich gas streams and are further surprisingly characterized by a higher “run-away” temperature. The catalyst formulations of the invention further may use very small quantities of ionic liquid (in the range of 3% by weight of the catalyst) to achieve these advantageous effects. The loss of catalyst activity is very small.

DETAILED DESCRIPTION OF THE INVENTION

The pre-formulated catalysts used for coating are, as already described above, supported palladium shell catalysts which preferably comprise at least one further promoter such as for example silver, gold, zinc, tin, lead, gallium, cadmium, copper, bismuth, or potassium. Preferred promoters are Ag, Au and Zn. Preferred metal or metal-alloy shell thicknesses are between 100 and 500 μm. The Pd metal content in relation to the total weight of the catalyst is between 10 and 1000 ppm, preferably between 50 and 500 ppm. For the desired target reaction the catalysts are used either as shaped bodies such as for example tablets, rings, tri-holes, extrudates etc., or as a granulate or powder. The mass ratio of palladium to promoter metal for example lies within a range of 1:5 to 3:1, preferably within a range of 1:4 to 2:1, and particularly preferably within a range of 1:3 to 1:1.

Suitable carrier substrates are Al₂O₃, SiO₂, alumo silicates, TiO₂, ZrO₂, ZnO, MgO, Fe₂O₃ and CeO₂, or mixtures thereof. In order to increase activity or selectivity the substrates can further be doped with at least one of the following elements: Li, Na, K, Rb, Cs, Be, Mg, Ca, Sr and/or Ba. Na, K and/or Ca are particularly suitable.

The BET surface area of the uncoated catalyst is ≦9 m²/g, and more preferably ≦8 m²/g, particularly preferably ≦6 m²/g. The determination of the surface area may be carried out in accordance with ASTM D3663, Standard Test Method for Surface Area of Catalysts and Catalyst Carriers.

The integral pore volume of the catalyst (determined according to DIN 66134 of February 1998 (N₂ adsorption)) without the IL-coating preferably is in the range of 0.005 to 0.07 ml/g, more preferably in the range of 0.007 to 0.04 ml/g and particularly preferably within a range of 0.009 to 0.02 ml/g.

Suitable pre-formulated catalysts for use in preparing supported ionic liquid phase catalyst compositions of the invention include any commercially-available supported Pd or Pd/Ag catalysts supplied by, for example Sud-Chemie, AG, Munich, Germany, BASF, Johnson-Mathey, etc.

For the production of a catalyst composition of the invention a pre-formulated catalyst is loaded with ionic liquid. The ionic liquid to be used for this is not particularly restricted, and in principle, all known ionic liquids suitable for this purpose can be used. Preferred ionic liquids for use with this invention are compounds with the formula (I):

[A]_(n) ⁺[Y]_(n) ⁻  (I),

wherein:

n=1 or 2;

[Y]_(n) ⁻ is selected from the group consisting of tetrafluoroborate ([BF₄]⁻), hexafluorophosphate ([PF₆]⁻), dicyanamide ([N(CN)₂]⁻), halides (Cl⁻, Br⁻, F⁻, I⁻), hexafluoroantimonate ([SbF₆]⁻), nitrate ([NO₃]⁻), nitrite ([NO₂]⁻), anionic metal complexes such as for example [CuCl₄]²⁻, [PdCl₄]²⁻ or [AuCl₄]⁻, acetate ([CH₃COO]⁻), trifluoracetate ([F3CCOO]⁻), hexafluoroarsenate ([AsF₆]⁻), sulfate ([SO₄]₂ ⁻), alkyl sulfates ([R′—SO₄]⁻), tosylate ([C₇H₇SO₃]⁻), triflate ([CF₃SO₃]⁻), nonaflate ([C₄F₉SO₃]⁻), triperfluoroethylene trifluorophosphate ([PF₃(C₂F₅)₃]⁻), tricyanomethide ([C(CN)₃]⁻), tetracyanoborate ([B(CN)₄]⁻, thiocyanate ([SCN]⁻), carbonate ([CO₃]₂ ⁻), carboxylates ([R′—COO]⁻), sulfonates ([R′SO₃]⁻), dialkylphosphates ([R′PO₄R″]⁻), alkyl phosphonates ([R′HPO₃]⁻) and bissulfonylimides ([(R′—SO₂)₂N]⁻), such as bis(trifluormethylsulfonyl)imide,

wherein R′ and R″ are the same or different, and each represents a linear or branched, 1 to 12 carbon atom-containing aliphatic or alicyclic alkyl group or a C₅-C₁₈-aryl, C₅-C₁₈-aryl-C₁-C₆-alkyl, or C₁-C₆-alkyl-C₅-C₁₈-aryl group that can be substituted with halogen atoms; and

[A]⁺ is selected from the group consisting of quaternary ammonium cations with the formula [NR¹R²R³R]⁺, phosphonium cations with the formula [PR¹R²R³R]⁺, sulfonium cations with the formula [SR¹R²R]⁺, guadinium cations with the formula (II):

imidazolium cations with the formula (III)

wherein the imidazole core may additionally be substituted with one or more groups selected from C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-aminoalkyl, C₅-C₁₂-aryl, and C₅-C₁₂-aryl-C₁-C₆-alkyl groups,

pyridinium cations with the formula (IV)

wherein the pyridine core may additionally be substituted with one or more groups selected from C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-aminoalkyl, C₅-C₁₂-aryl, and C₅-C₁₂-aryl-C₁-C₆-alkyl groups,

pyrazolium cations with the formula (V)

wherein the pyrazole core may additionally be substituted with one or more groups selected from C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-aminoalkyl, C₅-C₁₂-aryl, and C₅-C₁₂-aryl-C₁-C₆-alkyl groups,

triazolium cations with the formula (VI)

wherein the triazole core may additionally be substituted with one or more groups selected from C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-aminoalkyl, C₅-C₁₂-aryl, and C₅-C₁₂-aryl-C₁-C₆-alkyl groups,

and pyrrolidinium cations with the formula (VII)

wherein the pyrrolidinium core may additionally be substituted with one or more groups selected from C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-aminoalkyl, C₅-C₁₂-aryl, and C₅-C₁₂-aryl-C₁-C₆-alkyl groups,

wherein R¹, R², and R³ are selected independently from each other from the group consisting of: hydrogen; linear or branched, saturated or unsaturated, aliphatic or alicyclic alkyl groups with 1 to 20 carbon atoms, which may be interrupted by one or two of NH, O and/or S; heteroaryl groups with 3 to 8 carbon atoms and at least one hetero atom selected from N, O and S, wherein the heteroaryl groups can be substituted with one or more groups selected from C₁-C₆-alkyl groups and halogen atoms; heteroaryl-C₁-C₆-alkyl groups with 3 to 8 carbon atoms and at least one hetero atom selected from N, O and S in the heteroaryl portion, wherein the heteroaryl portion can be substituted with at least one group selected from C₁-C₆-alkyl groups and halogen atoms; polyethers with the formula [—CH₂CH₂O]_(n)R^(a) with n=1 to 50,000, wherein R^(a) is selected from the group consisting of linear or branched, saturated or unsaturated, aliphatic or alicyclic alkyl groups with 1 to 20 carbon atoms; aryl groups with 5 to 12 carbon atoms, which may be substituted with one or more C₁-C₆-alkyl groups and/or halogen atoms; aryl-C₁-C₆-alkyl groups with 5 to 12 carbon atoms in the aryl portion, which may be substituted with one or more C₁-C₆-alkyl groups and/or halogen atoms, and

wherein R is selected from the group consisting of: linear or branched, saturated or unsaturated, aliphatic or alicyclic alkyl groups with 1 to 20 carbon atoms; heteroaryl-C₁-C₆-alkyl groups with 4 to 8 carbon atoms and at least one hetero atom selected from N, O and S in the heteroaryl portion, which may be substituted with one or more C₁-C₆-alkyl groups and/or halogen atoms; and aryl-C₁-C₆-alkyl groups with 4 to 12 carbon atoms in the aryl portion, which may be substituted with one or more C₁-C₆-alkyl groups and/or halogen atoms.

Further preferred ionic liquids for use with this invention are compounds with the formula (I):

[A]_(n) ⁺[Y]_(n) ⁻  (I),

wherein:

n and [Y]_(n) ⁻ are as defined above, and

[A]⁺ is selected from the group consisting of quaternary ammonium cations with the formula [NR¹R²R³R]⁺, imidazolium cations with the formula (III)

pyridinium cations with the formula (IV)

and pyrrolidinium cations with the formula (VII)

wherein R, R¹, R² and R³ are selected independently from each other from the group consisting of hydrogen; linear or branched C₁-C₁₂-alkyl groups; linear or branched (C₁-C₆-alkyloxy)-C₁-C₆-alkyl groups; and aryl-C₁-C₆-alkyl groups with 5 to 12 carbon atoms in the aryl portion, which may be substituted with one or more C₁-C₆-alkyl groups and/or halogen atoms.

More preferred ionic liquids for preparing supported ionic liquid phase catalysts of the invention include 1-butyl-3-methylimidazolium triflate, 1-ethyl-3-methylpyridinium ethylsulfate, 1-butyl-1-methylpyrrolidinium triflate, 1-butyl-2,3-dimethylimidazolium triflate, 1-butyl-3-methylimidazolium tricyanomethane, 1-butyl-3-methylimidazolium methylsulfate, 1-butyl-3-methylimidazolium octylsulfate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methylimidazolium methylphosphonate, 1-ethyl-3-methylimidazolium triflate, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, 1-butyl-1-methylpyrrolidinium tetracyanoborate, 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium tricyanomethane, 1-ethyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium tetracyanoborate, 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, 1-ethyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide, 1-methyl-3-octylimidazolium triflate, ethyldimethyl-(2-methoxyethyl)ammonium tris(pentafluoroethyl)trifluorophosphate, tributylmethylammonium dicyanamide, tricyclohexyltetradecylphosphonium tris(pentafluoroethyl)trifluorophosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and mixtures thereof.

More preferred ionic liquids further include those of the formula (I), wherein [A]_(n) ⁺ is selected from the group consisting of 1-butyl-1-methylpyrrolidinium, 1-butyl-2,3-dimethylimidazolium, 1-butyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-ethyl-3-methylpyridinium, 1-methyl-3-octylimidazolium, ethyldimethyl-(2-methoxyethyl)ammonium, tributylmethylammonium, tricyclohexyltetradecylphosphonium, and mixtures thereof, and wherein [Y]_(n) ⁻ is selected from the group consisting of bis(trifluoromethylsulfonyl)imide, dicyanamide, ethylsulfate, methylphosphonate, methylsulfate, octylsulfate, tetracyanoborate, tetrafluoroborate, tricyanomethane, triflate, tris(pentafluoroethyl)trifluorophosphate, and mixtures thereof.

For the production of catalyst compositions of the invention, the ionic liquid or mixtures of several ionic liquids are dissolved or suspended in a solution agent suitable for the purpose, such as for example water, alcohols, acetone etc., or in a solution agent mixture, and applied continuously onto the already pre-formed catalyst inside a reaction chamber with the aid of a nozzle. For this the solution agent is continuously removed from the reaction chamber during the process. In order to achieve an even coating of the substrate, the substrate material is continuously fluidized through a process gas in a process known as fluidized bed coating. Further suitable coating processes are dip coating or spray application with a spray pistol or a spray drying pistol.

Apart from the application of ionic liquid by means of coating technologies, the same can also be applied by impregnating with a solution or suspension. For this the ionic liquid or mixtures of several ionic liquids are dissolved or suspended in a suitable solution agent (mixture) and subsequently brought into contact with the pre-formed catalyst. The solution agent is then removed under vacuum or at an increased temperature (or both), by resting in air, or by means of a gas stream. The quantity of solution agent used can be equal to or smaller or greater than the pore volume of the catalyst used.

The quantity of ionic liquid used is equal to or smaller than the pore volume of the catalyst used. After the application of the ionic liquid, one is left with an externally dry solid body coated with the desired quantity of ionic liquid. The pore volume of the resulting catalyst composition is reduced by the volume of the ionic liquid. Related to the total weight of the catalyst 0.1-5 wt. %, preferably 0.2-3 wt. %, and particularly preferably 0.3-1.5 wt. % of ionic liquid is used. The distribution of ionic liquid on the macroscopic substrate form body, granulate or powder is freely adjustable by selecting the coating conditions. Depending on the selection of the conditions, a formation of a so-called eggshell, egg-white, egg-yolk, or a uniform distribution of the ionic liquid may result on the substrate. In addition, any concentration gradient of ionic liquid can be created on the substrate. The ionic liquid is preferably applied to the substrate surface as a thin shell. The shell thickness of the ionic liquid on the substrate surface of this invention usually lies within a range of 10 to 2000 μm, preferably within a range of 20 to 1000 μm, and particularly preferably within a range of 50 to 250 μm.

The resulting catalyst can be used without restricting the target reaction. The reduction of metal particles required for activating the catalyst can either take place prior to a coating with the ionic liquid or following the same.

The catalyst can for example be reduced prior to coating with an ionic liquid. The methods to be used for the same are known to the expert, and can for example include wet chemical methods through reduction such as for example NaBH₄, LiAlH₄, hydrazine (hydrate), hypophosphite, formic acid, or salts of the same (formates). In addition a reduction can be brought about in the gaseous phase with hydrogen (in all mixtures with an inert gas; preferably 5% in N₂) within a temperature range of 50-200° C., preferably at 80-120° C.

The reduced metal particles obtained in this way usually have a diameter within a range of 1 to 30 nm, preferably within a range of 1 to 10 nm, and particularly preferably within a range of 2 to 8 nm.

EXAMPLES Example 1

Sample A contains 0.017 wt % Pd on 1-2 mm alumina spheres with a BET surface area of 4.0 m²/g. In order to make Sample A, 1100 g Alpha Alumina was added to 1075 mL PdCl₂ solution (0.178 mg Pd/mL) heated at 70° C. After the carrier was soaked in the solution for 1 hour, the solution was drained and then the catalyst was washed 10 times using 5 minute soak times with room temperature deionized water. After final wash, the catalyst was calcined in a muffle oven in air at 565° C. for 4 hours.

Sample A1 was made by adding 0.5 wt % of EMIM[EtSO₄] (1-ethyl-3-methylimidazolium ethylsulfate) on Sample A. In order to make Sample A1, Sample A (516.0 mg) was impregnated with an aqueous solution of 1-ethyl-3-methylimidazolium ethylsulfate (232 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A2 was made by adding 0.5 wt % of BMIM[OTf] (1-butyl-3-methylimidazolium triflate) on Sample A. In order to make Sample A2, Sample A (476.3 mg) was impregnated with an aqueous solution of 1-butyl-3-methylimidazolium triflate (214 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A3 was made by adding 0.5 wt % of BMPr[OTf] (1-butyl-1-methylpyrrolidinium triflate) on Sample A. In order to make Sample A3, Sample A (499.7 mg) was impregnated with an aqueous solution of 1-butyl-1-methylpyrrolidinium triflate (225 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A4 was made by adding 0.5 wt % of BMMIM[OTf] (1-Butyl-2,3-dimethylimidazolium triflate) on Sample A. In order to make Sample A4, Sample A (528.8 mg) was impregnated with an aqueous solution of 1-Butyl-2,3-dimethylimidazolium triflate (238 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A5 was made by adding 0.5 wt % of BMIM[BF₄] (1-butyl-3-methylimidazolium tetrafluoroborate) on Sample A. In order to make Sample A5, Sample A (508.2 mg) was impregnated with an aqueous solution of 1-butyl-3-methylimidazolium tetrafluoroborate (229 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A6 was made by adding 0.5 wt % of BMIM[MeSO₄] (1-butyl-3-methylimidazolium methylsulfate) on Sample A. In order to make Sample A6, Sample A (511.8 mg) was impregnated with an aqueous solution of 1-butyl-3-methylimidazolium methylsulfate (230 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A7 was made by adding 0.5 wt % of BMIM[C₈H₁₇SO₄] (1-butyl-3-methylimidazolium octylsulfate) on Sample A. In order to make Sample A7, Sample A (485.7 mg) was impregnated with an aqueous solution of 1-butyl-3-methylimidazolium octylsulfate (218 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A8 was made by adding 0.5 wt % of EMIM[OTf] (1-ethyl-3-methylimidazolium triflate) on Sample A. In order to make Sample A8, Sample A (509.9 mg) was impregnated with an aqueous solution of 1-ethyl-3-methylimidazolium triflate (229 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A9 was made by adding 0.5 wt % of EMPy[EtSO₄] (1-ethyl-3-methylpyridinium ethylsulfate) on Sample A. In order to make Sample A9, Sample A (504.0 mg) was impregnated with an aqueous solution of 1-ethyl-3-methylpyridinium ethylsulfate (227 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A10 was made by adding 0.5 wt % of EMIM[MePO₃] (1-ethyl-3-methylimidazolium methylphosphonate) on Sample A. In order to make Sample A10, Sample A (517.1 mg) was impregnated with an aqueous solution of 1-ethyl-3-methylimidazolium methylphosphonate (233 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A11 was made by adding 0.5 wt % of BMIM[C(CN)₃] (1-butyl-3-methylimidazolium tricyanomethane) on Sample A. In order to make Sample A11, Sample A (504.0 mg) was impregnated with a solution of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide in 2-butanone (227 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 60° C. for 4 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A12 was made by adding 0.5 wt % of BMIM[NTf₂] (1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) on Sample A. In order to make Sample A12, Sample A (513.4 mg) was impregnated with a solution of 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide in 2-butanone (231 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 60° C. for 4 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A13 was made by adding 0.5 wt % of MOIM[OTf] (1-methyl-3-octylimidazolium triflate) on Sample A. In order to make Sample A13, Sample A (502.1 mg) was impregnated with a solution of 1-methyl-3-octylimidazolium triflate in 2-butanone (226 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 60° C. for 4 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A14 was made by adding 0.5 wt % of EMIM[NTf₂] (1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide) on Sample A. In order to make Sample A14, Sample A (490.3 mg) was impregnated with a solution of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide in 2-butanone (220 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 60° C. for 4 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A15 was made by adding 0.5 wt % of EMIM[B(CN)₄] (1-ethyl-3-methylimidazolium tetracyanoborate) on Sample A. In order to make Sample A15, Sample A (504.8 mg) was impregnated with a solution of 1-ethyl-3-methylimidazolium tetracyanoborate in 2-butanone (227 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 60° C. for 4 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A16 was made by adding 0.5 wt % of EMIM[PF₃(C₂F₅)₃] (1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate) on Sample A. In order to make Sample A16, Sample A (514.4 mg) was impregnated with a solution of 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate in 2-butanone (231 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 60° C. for 4 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A17 was made by adding 0.5 wt % of EMPy[NTf₂] (1-ethyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide) on Sample A. In order to make Sample A17, Sample A (531.6 mg) was impregnated with a solution of 1-ethyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide in 2-butanone (239 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 60° C. for 4 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A18 was made by adding 0.5 wt % of BMPr[NTf₂] (1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide) on Sample A. In order to make Sample A18, Sample A (512.5 mg) was impregnated with a solution of 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide in 2-butanone (230 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 60° C. for 4 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A19 was made by adding 0.5 wt % of BMPr[PF₃(C₂F₅)₃] (1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate) on Sample A. In order to make Sample A19, Sample A (510.3 mg) was impregnated with a solution of 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate in 2-butanone (229 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 60° C. for 4 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A20 was made by adding 0.5 wt % of BMPr[B(CN)₄] (1-butyl-1-methylpyrrolidinium tetracyanoborate) on Sample A. In order to make Sample A20, Sample A (516.0 mg) was impregnated with a solution of 1-butyl-1-methylpyrrolidinium tetracyanoborate in 2-butanone (232 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 60° C. for 4 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A21 was made by adding 0.5 wt % of TBMA[N(CN)₂] (tributylmethylammonium dicyanamide) on Sample A. In order to make Sample A21, Sample A (474.2 mg) was impregnated with a solution of tributylmethylammonium dicyanamide in 2-butanone (213 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 60° C. for 4 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample A22 was made by adding 0.5 wt % of {EtMe₂(MeOEt)}N[PF₃(C₂F₅)₃] (ethyldimethyl-(2-methoxyethyl)ammonium tris(pentafluoroethyl)trifluorophosphate) on Sample A. In order to make Sample A22, Sample A (477.6 mg) was impregnated with a solution of ethyldimethyl-(2-methoxyethyl)ammonium tris(pentafluoroethyl)trifluorophosphate in 2-butanone (215 μL, 11.11 mg/mL) by incipient wetness. The catalyst was dried at 60° C. for 4 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Example 2

Sample B1 was made by adding 0.001 wt % of EMIM[EtSO₄] (1-ethyl-3-methylimidazolium ethylsulfate) on Sample A. In order to make Sample B1, Sample A (485.8 mg) was impregnated with an aqueous solution of 1-ethyl-3-methylimidazolium ethylsulfate (219 μL, 0.022 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample B2 was made by adding 0.007 wt % of EMIM[EtSO₄] (1-ethyl-3-methylimidazolium ethylsulfate) on Sample A. In order to make Sample B2, Sample A (505.1 mg) was impregnated with an aqueous solution of 1-ethyl-3-methylimidazolium ethylsulfate (227 μL, 0.16 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample B3 was made by adding 0.025 wt % of EMIM[EtSO₄] (1-ethyl-3-methylimidazolium ethylsulfate) on Sample A. In order to make Sample B3, Sample A (512.8 mg) was impregnated with an aqueous solution of 1-ethyl-3-methylimidazolium ethylsulfate (231 μL, 0.56 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample B4 was made by adding 0.05 wt % of EMIM[EtSO₄] (1-ethyl-3-methylimidazolium ethylsulfate) on Sample A. In order to make Sample B4, Sample A (468.0 mg) was impregnated with an aqueous solution of 1-ethyl-3-methylimidazolium ethylsulfate (210 μL, 1.11 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample B5 was made by adding 0.1 wt % of EMIM[EtSO₄] (1-ethyl-3-methylimidazolium ethylsulfate) on Sample E. In order to make Sample B5, Sample A (497.3 mg) was impregnated with an aqueous solution of 1-ethyl-3-methylimidazolium ethylsulfate (224 μL, 2.22 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Sample B6 was made by adding 0.25 wt % of EMIM[EtSO4] (1-ethyl-3-methylimidazolium ethylsulfate) on Sample A. In order to make Sample B6, Sample A (480.9 mg) was impregnated with an aqueous solution of 1-ethyl-3-methylimidazolium ethylsulfate (216 μL, 5.56 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Comparative Example 3

Comparative Sample C contains 0.019 wt % Pd on 1-2 mm alumina spheres with a BET surface area of 50 m²/g. In order to make Comparative Sample C, 10 g alumina was added to 11.4 mL PdCl₂ solution (0.1667 mg Pd/mL) heated at 70° C. After the carrier was soaked in the solution for 1 hour, the solution was withdrawn and then the catalyst was washed 10 times using 5 minute soak times with room temperature deionized water. After the final washing step, the catalyst was calcined in muffle oven in air at 565° C. for 4 hours.

Comparative Sample C1 was made by adding 0.5 wt % of EMIM[EtSO₄] (1-ethyl-3-methylimidazolium ethylsulfate) on Comparative Sample C. In order to make Comparative Sample C1, Comparative Sample C (502.1 mg) was impregnated with an aqueous solution of 1-ethyl-3-methylimidazolium ethylsulfate (316 μL, 7.94 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Comparative Sample C2 was made by adding 0.5 wt % of BMIM[OTf] (1-butyl-3-methylimidazolium triflate) on Comparative Sample C. In order to make Comparative Sample C2, Comparative Sample C (484.4 mg) was impregnated with an aqueous solution of 1-butyl-3-methylimidazolium triflate (305 μL, 7.94 mg/mL) by incipient wetness. The catalyst was dried at 80° C. for 16 hours and reduced at 100° C. in 5% H₂/N₂ for 1 hour.

Example 4

Sample A, Samples A1-A22, Samples B1-B6, and Comparative Samples C, C1 and C2 were tested as prepared in a microreactor test unit at typical front-end hydrogenation conditions. In the test, a simulated de-propanizer feed containing 0.35 mol % acetylene, 15 mol % hydrogen, 0.02 mol % CO, 47 mol % ethylene, and balance nitrogen was passed over a 260 μl catalyst bed at 478 psig (34 bar) in total pressure and 7000 h⁻¹ in Gas Hourly Space Velocity (GHSV), while the bed temperature was gradually increased from about 45° C. The acetylene concentration at the reactor outlet was monitored with an on-line gas chromatograph (GC). The acetylene concentration at reactor outlet continued decreasing with increasing temperature until reaching <25 ppm. The temperature at this point was defined as the “clean up temperature” (T1). Catalyst bed temperature was further increased until 125° C. (the maximum temperature the test unit could reach) or a certain temperature (T2), at which the outlet ethane concentration was >2% due to the increased non-selective reaction of hydrogen with ethylene. The temperature range between T1 and T2 is called the “operation window”. Test results of Sample A, Samples A1 to A22, Samples B1-B6, as well as of Comparative Sample C, C1-C2 are listed in the table below. For catalysts that did not run away at the maximum temperature the test unit could reach, T2 was calculated by fitting the data at temperatures above complete acetylene conversion with a first order kinetic model.

Test Results of Samples A, A1 to A22, B1 to B6, and Comparative Samples C and C1 to C2 Operation Selectivity Ethane T1 T2 Window at Make at [° C.] [° C.] [° C.] T1 [%] [125° C.] Sample A 63  84 21 92.8 10.439 Sample A1 68 176 108  96.1 0.429 Sample A2 68 137 69 96.9 0.714 Sample A3 61 113 52 89.0 3.316 Sample A4 62 113 51 85.6 3.228 Sample A5 69 164 95 94.5 0.462 Sample A6 68 167 99 97.6 0.390 Sample A7 68 157 89 95.5 0.594 Sample A8 65 141 76 96.2 1.139 Sample A9 65 100 35 95.8 9.45 Sample A10 82 188 106  90.1 0.194 Sample A11 68 157 89 90.0 0.637 Sample A12 61 100 39 89.5 4.668 Sample A13 67 115 48 66.1 3.005 Sample A14 60 110 50 99.8 3.477 Sample A15 71 149 78 90.6 0.821 Sample A16 67 145 78 90.1 1.199 Sample A17 62  86 24 93.0 10.23 Sample A18 64 101 37 88.9 4.836 Sample A19 62 120 58 74.8 2.382 Sample A20 69 150 81 98.9 0.906 Sample A21 65 153 88 85.2 0.982 Sample A22 66 122 56 93.2 2.315 Sample B1 62  82 20 47.3 10.444 Sample B2 63 101 38 69.0 8.691 Sample B3 60 113 53 96.3 9.122 Sample B4 61 119 58 95.5 5.378 Sample B5 65 121 56 98.4 3.838 Sample B6 67 123 56 100 2.428 Comparative 56  76 20 91.1 10.506 Sample C Comparative 68  99 31 81.3 5.725 Sample C1 Comparative 65  98 33 96.1 6.878 Sample C2 The operation window as well as the selectivity markedly increase with decrease in BET surface area (Samples A1 and A2 compared to Comparative Samples C1 and C2).

Example 5

Sample D is a commercial selective hydrogenation catalyst that is supplied by Süd-Chemie AG under trade name OleMax® 251. It contains 0.019 wt % Pd and 0.05 wt % Ag on 4×4 mm alumina tablets with a BET surface area of about 4.0 m²/g.

Sample D1 was made by adding 0.5 wt % of BMMIM[OTf] (1-Butyl-2,3-dimethylimidazolium triflate) on Sample D. In order to make Sample D1, 0.6 g of the ionic liquid BMMIM[OTf] were dissolved in 150 ml deionized water. At the same time 120 g of the dry Sample D is fluidized in a reaction chamber with synthetic air as the process gas. The solution of BMMIM[OTf] in water was introduced into the reaction chamber at a flow rate of 5 ml/min via a feed pump and sprayed onto the solid catalyst via a spray nozzle at a temperature of 80° C. Once the entire solution has been applied and the substrate is dry, the catalyst formulation is further dried at 80° C. for 2 hours.

Sample D2 was made by adding 1.0 wt % of BMMIM[OTf] (1-Butyl-2,3-dimethylimidazolium triflate) on Sample D. In order to make Sample D2, 1.2 g of the ionic liquid BMMIM[OTf] were dissolved in 150 ml deionized water. At the same time 120 g of the dry Sample D is fluidized in a reaction chamber with synthetic air as the process gas. The solution of BMMIM[OTf] in water was introduced into the reaction chamber at a flow rate of 5 ml/min via a feed pump and sprayed onto the solid catalyst via a spray nozzle at a temperature of 80° C. Once the entire solution has been applied and the substrate is dry, the catalyst formulation is further dried at 80° C. for 2 hours.

Sample D3 was made by adding 2.0 wt % of BMMIM[OTf] (1-Butyl-2,3-dimethylimidazolium triflate) on Sample D. In order to make Sample D3, 2.4 g of the ionic liquid BMMIM[OTf] were dissolved in 150 ml deionized water. At the same time 120 g of the dry Sample D is fluidized in a reaction chamber with synthetic air as the process gas. The solution of BMMIM[OTf] in water was introduced into the reaction chamber at a flow rate of 5 ml/min via a feed pump and sprayed onto the solid catalyst via a spray nozzle at a temperature of 80° C. Once the entire solution has been applied and the substrate is dry, the catalyst formulation is further dried at 80° C. for 2 hours.

Sample D4 was made by adding 3.0 wt % of BMMIM[OTf] (1-Butyl-2,3-dimethylimidazolium triflate) on Sample D. In order to make Sample D4, 3.6 g of the ionic liquid BMMIM[OTf] were dissolved in 150 ml deionized water. At the same time 120 g of the dry Sample D is fluidized in a reaction chamber with synthetic air as the process gas. The solution of BMMIM[OTf] in water was introduced into the reaction chamber at a flow rate of 5 ml/min via a feed pump and sprayed onto the solid catalyst via a spray nozzle at a temperature of 80° C. Once the entire solution has been applied and the substrate is dry, the catalyst formulation is further dried at 80° C. for 2 hours.

Sample D1′ was made by impregnation of Sample D with a BMMIM[OTf] (1-Butyl-2,3-dimethylimidazolium triflate) solution containing 0.5 g of BMMIM[OTf] in 38 ml deionized water. The clear solution is added to 120 g of dry Sample D. The mixture is then mixed at room temperature for approx. 60 minutes. The catalyst formulation is then dried at 80° C. for 16 h to finally obtain Sample D1′.

Example 6

Samples prepared in Example 5 were tested as prepared in a bench scale test unit at typical front-end hydrogenation conditions. In the test, a simulated de-ethanizer feed containing 0.35 mol % acetylene, 20 mol % hydrogen, 0.02 mol % CO, 45 mol % ethylene, and balance methane was passed over a 25 ml catalyst bed at 500 psig (35.5 bar) in total pressure and 7000 h⁻¹ in Gas Hourly Space Velocity (GHSV), while the bed temperature was gradually increased from about 35° C. The acetylene concentration at the reactor outlet was monitored with an on-line gas chromatograph (GC). The acetylene concentration at reactor outlet continued decreasing with increasing temperature until reaching <25 ppm. The temperature at this point was defined as the “clean up temperature” (T1). Catalyst bed temperature was further increased until 105° C. (the maximum temperature the water bath could reach) or a certain temperature (T2), at which the outlet ethane concentration was >2% due to the increased non-selective reaction of hydrogen with ethylene. The temperature range between T1 and T2 is called the “operation window”. Test results of Sample D and Samples D1 to D4 and D1′ are listed in the table below.

Front End Deethanizer Feed Test Results Operation Selectivity T1 T2 Window at T1 [° C.] [° C.] [° C.] [%] Sample D 52 57 5 −1 Sample D1 61 97 36 52 Sample D2 61 105 44 61 Sample D3 69 >105 >36 48 Sample D4 73 >105 >32 56 Sample D1′ 67 99 32 38

The operation window as well as the selectivity markedly increase with increasing BMMIM[OTf] content. The optimum BMMIM[OTf] loading seems to be 0.5-1%. At higher loading, the runaway temperature continued to increase at the expense of a higher T1 temperature. Adding BMMIM[OTf] onto Sample D can be realized by coating or wet impregnation; and both methods can generate a new catalyst with significantly improved operation window.

Example 7

Sample E is a commercial front end selective hydrogenation catalyst that is supplied by Süd-Chemie AG under the trade name OleMax® 250. It contains 0.018 wt % Pd on 4×4 mm alumina tablets with a BET surface area of about 4.0 m²/g.

Sample E1 was made by adding 1.0 wt % of BMMIM[OTf] (1-Butyl-2,3-dimethylimidazolium triflate) on Sample E. In order to make Sample E1, 1.2 g of the ionic liquid BMMIM[OTf] were dissolved in 150 ml deionized water. At the same time 120 g of the dry Sample E is fluidized in a reaction chamber with synthetic air as the process gas. The solution of BMMIM[OTf] in water was introduced into the reaction chamber at a flow rate of 5 ml/min via a feed pump and sprayed onto the solid catalyst via a spray nozzle at a temperature of 80° C. Once the entire solution has been applied and the substrate is dry, the catalyst formulation is further dried at 80° C. for 2 hours.

Sample E2 was made by adding 2.0 wt % of BMMIM[OTf] (1-Butyl-2,3-dimethylimidazolium triflate) on Sample E. In order to make Sample E2, 2.4 g of the ionic liquid BMMIM[OTf] were dissolved in 150 ml deionized water. At the same time 120 g of the dry Sample E is fluidized in a reaction chamber with synthetic air as the process gas. The solution of BMMIM[OTf] in water was introduced into the reaction chamber at a flow rate of 5 ml/min via a feed pump and sprayed onto the solid catalyst via a spray nozzle at a temperature of 80° C. Once the entire solution has been applied and the substrate is dry, the catalyst formulation is further dried at 80° C. for 2 hours.

Sample E3 was made by adding 3.0 wt % of BMMIM[OTf] (1-Butyl-2,3-dimethylimidazolium triflate) on Sample E. In order to make Sample E3, 3.6 g of the ionic liquid BMMIM[OTf] were dissolved in 150 ml deionized water. At the same time 120 g of the dry Sample E is fluidized in a reaction chamber with synthetic air as the process gas. The solution of BMMIM[OTf] in water was introduced into the reaction chamber at a flow rate of 5 ml/min via a feed pump and sprayed onto the solid catalyst via a spray nozzle at a temperature of 80° C. Once the entire solution has been applied and the substrate is dry, the catalyst formulation is further dried at 80° C. for 2 hours.

Example 8

Sample E, Sample E1, Sample E2 and Sample E3 were tested after in-situ reduction at 94° C. for 1 hour in a bench scale test unit at typical front-end hydrogenation conditions. In the test, a simulated de-ethanizer feed containing 0.35 mol % acetylene, 20 mol % hydrogen, 0.02 mol % CO, 45 mol % ethylene, and balance methane was passed over a 25 ml catalyst bed at 500 psig (35.5 bar) in total pressure and 7000 h⁻¹ in Gas Hourly Space Velocity (GHSV), while the bed temperature was gradually increased from about 35° C. The acetylene concentration at the reactor outlet was monitored with an on-line gas chromatograph (GC). The acetylene concentration at reactor outlet continued decreasing with increasing temperature until reaching <25 ppm. The temperature at this point was defined as the “clean up temperature” (T1). Catalyst bed temperature was further increased until 105° C. (the maximum temperature the water bath could reach) or a certain temperature (T2), at which the outlet ethane concentration was >2% due to the increased non-selective reaction of hydrogen with ethylene. The temperature range between T1 and T2 is called the “operation window”. Test results of Sample E and Samples E1 to E3 are listed in the table below.

Test Results of Sample E and Samples El to E3 Operation Selectivity T1 T2 Window at T1 [° C.] [° C.] [° C.] [%] Sample E 53 62  9 58 Sample E1 53 69 16 65 Sample E2 52 81 29 74 Sample E3 62 92 30 78

Upon addition of BMMIM[OTf] onto the Pd/alumina catalyst, the operation window increases linearly up to a loading of 2% and then stays constant at 30° C. At higher loading, both T1 and operation window increased.

Example 9

Comparative Sample F is a commercial selective hydrogenation catalyst that is supplied by Süd-Chemie AG under trade name OleMax® 201. It contains 0.03 wt % Pd and 0.18 wt % Ag on 2-4 mm alumina spheres with a BET surface area of about 35 m²/g.

Comparative Sample F1′ was made by adding 0.5 wt % of EMIM[EtSO₄] (1-ethyl-3-methylimidazolium ethylsulfate) onto Sample F by incipient wetness impregnation method. The EMIM[EtSO₄] solution contains 0.5 g of EMIM[EtSO₄] in 60 ml deionized water. The clear solution was added to 100 g of Comparative Sample F and mixed for about 5 min. The catalyst formulation is then dried at 80° C. for 16 hr to obtain the final product.

Comparative Sample F2′ was made by adding 1.0 wt % of EMIM[EtSO₄] (1-ethyl-3-methylimidazolium ethylsulfate) onto Sample F by incipient wetness impregnation method. The EMIM[EtSO₄] solution contains 1 g of EMIM[EtSO₄] in 60 ml deionized water. The clear solution was added to 100 g of Comparative Sample F and mixed for about 5 min. The catalyst formulation is then dried at 80° C. for 16 hr to obtain final product.

Sample D2′ was made by adding 0.5 wt % EMIM[EtSO₄] (1-ethyl-3-methylimidazolium ethylsulfate) on Sample D by incipient wetness impregnation. The EMIM[EtSO₄] solution contains 0.5 g of EMIM[EtSO₄] in 24 ml deionized water. The clear solution was added to 100 g of Sample D and mixed for about 5 min. The catalyst formulation is then dried at 80° C. for 16 hr to obtain final product.

Sample D3′ was made by adding 1 wt % EMIM[EtSO₄] (1-ethyl-3-methylimidazolium ethylsulfate) on Sample D by incipient wetness impregnation. The EMIM[EtSO₄] solution contains 1 g of EMIM[EtSO₄] in 24 ml deionized water. The clear solution was added to 100 g of Sample D and mixed for about 5 min. The catalyst formulation is then dried at 80° C. for 16 hr to obtain final product.

Example 10

Samples and Comparative Samples prepared in Example 9 were tested as prepared in a bench scale test unit at typical front-end hydrogenation conditions. In the test, a simulated de-ethanizer feed containing 0.35 mol % acetylene, 20 mol % hydrogen, 0.02 mol % CO, 45 mol % ethylene, and balance methane was passed over a 25 ml catalyst bed at 500 psig (35.5 bar) in total pressure and 7000 h⁻¹ in Gas Hourly Space Velocity (GHSV), while the bed temperature was gradually increased from about 35° C. The acetylene concentration at the reactor outlet was monitored with an on-line gas chromatograph (GC). The acetylene concentration at reactor outlet continued decreasing with increasing temperature until reaching <25 ppm. The temperature at this point was defined as the “clean up temperature” (T1). Catalyst bed temperature was further increased until 105° C. (the maximum temperature the water bath could reach) or a certain temperature (T2), at which the outlet ethane concentration was >2% due to the increased non-selective reaction of hydrogen with ethylene. The temperature range between T1 and T2 is called the “operation window”. Test results of Sample F2′ and F3′ did not run away at the maximum temperature the test unit could reach: the ethane make was 0.35% at 102° C. for both catalysts. Their T2's for 2% ethane make were calculated by fitting the data at temperatures above complete acetylene conversion with a first order kinetic model.

Front End Deethanizer Feed Test Results Selectivity Ethane T1 T2 T2-T1 at T1 Make at [° C.] [° C.] [° C.] [%] 102° C. [%] Sample F 51 53  2 −5 Not operable Sample F1′ 54 75 21 76 Not operable Sample F2′ 59 80 21 86 Not operable Sample D 52 57  5 −1 Not operable Sample D2′ 65 148 83 91 0.35 Sample D3′ 66 149 83 94 0.35 It appears that EMIM[EtSO₄] has much lower impact on Sample F than on Sample D. 

What is claimed:
 1. A catalyst comprising palladium supported on a substrate, said catalyst further comprising at least one ionic liquid, wherein said substrate has a BET surface area of less than 9 m²/g prior to the addition of said at least one ionic liquid.
 2. The catalyst of claim 1, wherein said BET surface area is preferably within a range of 2 to 8 m²/g, and more preferably within a range of 3 to 5 m²/g.
 3. The catalyst of claim 1, wherein the palladium-supported catalyst further comprises a promoter selected from the group consisting of Ag, Au, Zn, Sn, Cd, Pb, Cu, Bi, K, Ga, and mixtures thereof.
 4. The catalyst of claim 3, wherein the promoter comprises Ag.
 5. The catalyst of claim 1, having a Pd loading of 10 to 1000 ppm.
 6. The catalyst of claim 3, having a ratio of Pd:promoter of 1:5-3:1.
 7. The catalyst of claim 1, wherein the ionic liquid comprises a compound of the formula: [A]_(n) ⁺[Y]_(n) ⁻, wherein: n=1 or 2; [Y]_(n) ⁻ is selected from the group consisting of tetrafluoroborate ([BF₄]⁻) hexafluorophosphate ([PF₆]⁻), dicyanamide ([N(CN)₂]⁻), halides (Cl⁻, Br⁻, F⁻, I⁻), hexafluoroantimonate ([SbF₆]⁻), nitrate ([NO₃]⁻), nitrite ([NO₂]⁻), anionic metal complexes such as for example [CuCl₄]²⁻, [PdCl₄]²⁻ or [AuCl₄]⁻, acetate ([CH₃COO]⁻), trifluoracetate ([F₃CCOO]⁻), hexafluoroarsenate ([AsF₆]⁻), sulfate ([SO₄]2⁻), hydrogen sulfate ([R′—SO₄]⁻), alkyl sulfate ([R′—SO₄]⁻), tosylate ([C₇H₇SO₃]⁻), triflate ([CF₃SO₃]⁻), nonaflate ([C₄F₉SO₃]⁻), triperfluoroethylene trifluorophosphate ([PF₃(C₂F₅)₃]⁻), tricyanomethide ([C(CN)₃]⁻), tetracyanoborate ([B(CN)₄]⁻, thiocyanate ([SCN]⁻), carbonate ([CO₃]₂ ⁻), carboxylate ([R′—COO]⁻), sulfonate ([R′SO₃]⁻), dialkylphosphate ([R′PO₄R″]⁻), alkyl phosphonate ([R′HPO₃]⁻) and bissulfonylimide ([(R′-SO₂)₂N]⁻), such as bis(trifluormethylsulfonyl)imide, wherein R′ and R″ are the same or different, and each represent a linear or branched 1 to 12 carbon atom-containing aliphatic or alicyclic alkyl group or a C₅-C₁₈-aryl, C₅-C₁₈-aryl-C₁-C₆-alkyl or C₁-C₆-alkyl-C₅-C₁₈-aryl group that can be substituted with halogen atoms; [A]⁺ is selected from the group consisting of quaternary ammonium cations with the formula [NR¹R²R³R]⁺, phosphonium cations with the formula [PR¹R²R³R]⁺, sulfonium cations with the formula [SR¹R²R]⁺, guadinium cations with the formula

imidazolium cations with the formula

wherein the imidazole core can also be substituted with one or more groups selected from C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-aminoalkyl, C₅-C₁₂-aryl and C₅-C₁₂-aryl-C₁-C₆-alkyl groups, pyridinium cations with the formula

wherein the pyridine core can also be substituted with one or more groups selected from C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-aminoalkyl, C₅-C₁₂-aryl and C₅-C₁₂-aryl-C₁-C₆-alkyl groups, pyrazolium cations with the formula

wherein the pyrazole core can also be substituted with one or more groups selected from C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-aminoalkyl, C₅-C₁₂-aryl or C₅-C₁₂-aryl-C₁-C₆-alkyl groups, and triazolium cations with the formula

wherein the triazole core can also be substituted with one or more groups selected from C₁-C₆-alkyl, C₁-C₆-alkoxy, C₁-C₆-aminoalkyl, C₅-C₁₂-aryl or C₅-C₁₂-aryl-C₁-C₆-alkyl groups, wherein R¹, R², R³ are selected independently from each other from the group consisting of: hydrogen; linear or branched, saturated or unsaturated, aliphatic or alicyclic alkyl groups with 1 to 20 carbon atoms; heteroaryl groups with 3 to 8 carbon atoms and at least one hetero atom selected from N, O and S, wherein the heteroaryl group can be substituted with one or more groups selected from C₁-C₆-alkyl groups and halogen atoms; heteroaryl-C₁-C₆-alkyl groups with 3 to 8 carbon atoms and at least one hetero atom selected from N, O and S in the heteroaryl moiety, wherein the heteroaryl moiety can be substituted with at least one group selected from C₁-C₆-alkyl groups and halogen atoms; polyethers with the formula [—CH₂CH₂O]_(n)R^(a) with n=1 to 50,000, wherein R^(a) is selected from the group consisting of linear or branched, saturated or unsaturated, aliphatic or alicyclic alkyl groups with 1 to 20 carbon atoms; aryl groups with 5 to 12 carbon atoms, which may be substituted with one or more C₁-C₆-alkyl groups and/or halogen atoms; aryl-C₁-C₆-alkyl groups with 5 to 12 carbon atoms in the aryl moiety, which may be substituted with one or more C₁-C₆-alkyl groups and/or halogen atoms, and wherein R is selected from the group consisting of: linear or branched, saturated or unsaturated, aliphatic or alicyclic alkyl groups with 1 to 20 carbon atoms; heteroaryl-C₁-C₆-alkyl groups with 4 to 8 carbon atoms and at least one hetero atom selected from N, O and S in the heteroaryl moiety, which can be substituted with one or more C₁-C₆-alkyl groups and/or halogen atoms; and aryl-C₁-C₆-alkyl groups with 4 to 12 carbon atoms in the aryl moiety, which may be substituted with one or more C₁-C₆-alkyl groups and/or halogen atoms.
 8. The catalyst of claim 7, wherein the ionic liquid comprises one or more selected from the group consisting of 1-butyl-3-methylimidazolium triflate, 1-ethyl-3-methylpyridinium ethylsulfate, 1-butyl-1-methylpyrrolidinium triflate, 1-butyl-2,3-dimethylimidazolium triflate, 1-butyl-3-methylimidazolium tricyanomethane, 1-butyl-3-methylimidazolium methylsulfate, 1-butyl-3-methylimidazolium octylsulfate, 1-butyl-3-methylimidazolium tetrafluoroborate, 1-ethyl-3-methylimidazolium ethylsulfate, 1-ethyl-3-methylimidazolium methylphosphonate, 1-ethyl-3-methylimidazolium triflate, 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide, 1-butyl-1-methylpyrrolidinium tetracyanoborate, 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate, 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, 1-butyl-3-methylimidazolium tricyanomethane, 1-ethyl-3-methylpyridinium bis(trifluoromethylsulfonyl)imide, 1-ethyl-3-methylimidazolium tetracyanoborate, 1-ethyl-3-methylimidazolium tris(pentafluoroethyl)trifluorophosphate, 1-methyl-3-octylimidazolium triflate, ethyldimethyl-(2-methoxyethyl)ammonium tris(pentafluoroethyl)trifluorophosphate, tributylmethylammonium dicyanamide, tricyclohexyltetradecylphosphonium tris(pentafluoroethyl)trifluorophosphate, 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide, and mixtures thereof.
 9. The catalyst of claim 7, wherein [A]_(n) ⁺ is selected from the group consisting of 1-butyl-1-methylpyrrolidinium, 1-butyl-2,3-dimethylimidazolium, 1-butyl-3-methylimidazolium, 1-ethyl-3-methylimidazolium, 1-ethyl-3-methylpyridinium, 1-methyl-3-octylimidazolium, ethyldimethyl-(2-methoxyethyl)ammonium, tributylmethylammonium, tricyclohexyltetradecylphosphonium, and mixtures thereof, and wherein [Y]_(n) ⁻ is selected from the group consisting of bis(trifluoromethylsulfonyl)imide, dicyanamide, ethylsulfate, methylphosphonate, methylsulfate, octylsulfate, tetracyanoborate, tetrafluoroborate, tricyanomethane, triflate, tris(pentafluoroethyl)trifluorophosphate, and mixtures thereof.
 10. The catalyst of claim 1, having an ionic liquid loading of 0.01% to 10% by weight, and more preferably of 0.1% to 5% by weight.
 11. The catalyst of claim 1, having a cleanup temperature of less than 80° C. and an operating window of greater than 25° C. when tested with a simulated de-ethanizer feed containing 0.35 mol % acetylene, 20 mol % hydrogen, 0.02 mol % CO, 45 mol % ethylene, and balance methane being passed over a 25 ml catalyst bed at 500 psig (35.5 bar) in total pressure and 7000 h⁻¹ in Gas Hourly Space Velocity (GHSV), while the bed temperature is gradually increased from about 35° C., the “clean up temperature” is defined as the temperature at which the outlet reaches <25 ppm acetylene, the runaway temperature is defined as the temperature at which the outlet ethane concentration is >2% and the operation window is defined as the difference between the runaway temperature and the clean up temperature.
 12. The catalyst of claim 1, wherein the integral pore volume of the catalyst without the presence of said at least one ionic liquid is in the range of 0.005 to 0.07 ml/g, preferably in the range of 0.007 to 0.04 ml/g and more preferably within a range of 0.009 to 0.02 ml/g.
 13. The catalyst of claim 1, having a selectivity of >25% at clean up temperature, when tested with a simulated de-ethanizer feed containing 0.35 mol % acetylene, 20 mol % hydrogen, 0.02 mol % CO, 45 mol % ethylene, and balance methane being passed over a 25 ml catalyst bed at 500 psig (35.5 bar) in total pressure and 7000 h⁻¹ in Gas Hourly Space Velocity (GHSV), while the bed temperature is gradually increased from about 35° C., the “clean up temperature” being defined as the temperature at which the outlet reaches <25 ppm acetylene.
 14. A method of making a coated catalyst, comprising the steps of: (a) providing a catalyst having a BET surface area less than or equal to 9 m²/g and comprising palladium supported on a substrate and optionally further comprising a promoter; (b) coating the catalyst in (a) with a mixture of an ionic liquid and a solution agent; and (c) removing the solution agent during or after the coating in (b).
 15. The process of claim 14, further comprising the step of reducing the catalyst before step (b) or after step (c).
 16. The process of claim 14, wherein step (b) comprises a fluidized bed coating or an impregnation with a solution or suspension.
 17. A method of selective hydrogenation of acetylene in front-end mixed olefin feed streams, comprising catalyzing said hydrogenation with a catalyst comprising palladium supported on a substrate, the catalyst having an uncoated BET surface area of less than 9 m²/g, said catalyst further comprising at least one ionic liquid.
 18. The method of claim 17, wherein the selective hydrogenation occurs in a gas phase.
 19. The method of claim 17, wherein the selective hydrogenation occurs in a liquid phase. 